Preventing Childhood Obesity - Evidence Policy and Practice.pdf

Chapter 21
determinants and tobacco control policy responses
and tobacco industry activities.
The WHO STEPwise approach to Surveillance
( STEPS ) is another example of standardized international
monitoring activities of risk factors for chronic
diseases. It is described as a standardized method for
collecting, analysing and disseminating data in WHO
member countries. 3
By using the same standardized questions and
protocols, all countries can use STEPS information
not only for monitoring within - country trends, but
also for making comparisons across countries. The
approach encourages the collection of small amounts
of useful information on a regular and continuing
basis.
3
This chapter does not use the term “ surveillance ”
but rather addresses systematic collection and analysis
of data as “monitoring ” , and identifies individuals for
interventions as “screening ” .
Purposes of m onitoring
Monitoring of o besity t rends; p rediction of
f uture p revalence and h ealth i mpact
The common form of monitoring is the analyses and
interpretation of routine cross - sectionally collected
data on indicators of overweight and obesity. These
include weight and height derived indices such as BMI
or waist circumference.
The monitoring (repeated prevalence data) of BMI in
children could lead to the following benefits: 4
• describing trends in weight status over time among
populations and/or subpopulations at a school,
district, state or nationwide level;
• creating awareness among school and health
personnel, community members, and policy makers
to the extent of weight problems in specific
populations;
• driving improvement in policies, practices and services
to prevent and treat obesity;
• monitoring the effects of school-based physical
activity and nutrition programs/policies;
• monitoring progress toward achieving national
health objectives or relevant state or local health
objectives related to childhood obesity.
Well - known examples of monitoring systems that
have included indicators of obesity are the National
Health and Nutrition Examination Survey s ( NHANES )
in the United States.
NHANES has been an exemplary system historically
as well as currently and has some unique features
so it is described in some detail. Since its inception in
1959, eight separate Health Examination Surveys have
been conducted and over 130,000 people have served
as survey participants.
The first three National Health Surveys — National
Health Examination Survey ( NHES ) I, II, and III —
were conducted between 1959 and 1970. In 1969 it
was decided that the National Nutrition Surveillance
System would be combined with the National Health
Examination Survey, thereby forming the National
Health and Nutrition Examination Survey, or
NHANES.
Five NHANES have been conducted since 1970.
NHANES I (1971 – 1975), NHANES II (1976 – 1980),
the Hispanic Health and Nutrition Examination
Survey ( HHANES 1982 – 1984), NHANES III
(1988 – 1994).
Beginning in 1999, NHANES became a continuous
survey. In 1999, 64% of the US population was
overweight or obese, while the prevalence of obesity
among children and adolescents had more than
doubled during the previous two decades. Since then,
further moderate increases have been observed, but
there now seems to be a gradual leveling off in the
trends.
The NHANES surveys have very high response rates
(94 – 97%) and are based on measured weights and
heights rather than being self - reported. For example,
the Behavioral Risk Factor Surveillance System is the
basis for the maps of the USA with states changing
color over time indicating an increasing prevalence of
obesity. In this Survey, which is based on self - reported
heights and weights in adults in a nationwide telephone
survey, it was found that the prevalence of
obesity in 1999 was 18.9%. 5 At the same time, the
prevalence of obesity in the NHANES was 30.5%. 6
This profound difference illustrates that sampling and
methodology may have important implications for
assessing the problem of obesity. Misreporting of
weight and heights are not only problems in surveys
in adults. It has been shown that one quarter to one
half of overweight adolescents would be missed if
based exclusively on self - reported data. 7 Actual and
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